A boy with his younger brother. [Photo provided to chinadaily.com.cn]

Chinese lawmakers passed a historic decision on Sunday, allowing all couples to have two children.

"The state advocates that one couple shall be allowed to have two children," according to the newly revised Law on Population and Family Planning, passed at the bi-monthly session of the National People's Congress Standing Committee, which ran from Monday to Sunday.

The newly revised law will take effect on Jan. 1.

Relaxation of the family planning policy is expected to provide part of the solution to the challenge of an aging population, and to become a new driver for the economy in the long run.

By the end of 2014, the number of people over 60 years of age had reached 212 million, accounting for 15.5 percent of the total population. Of those, about 40 million were disabled or partly disabled.

The new two-child policy could increase economic growth rate by 0.5 percentage points through reducing China's dependency ratio, said National Health and Family Planning Commission in November.

The change in policy is expected to mean over 30 million more people in the labor force by 2050 and an decrease of 2 percentage points in the share of elderly of Chinese population, said Wang Pei'an,deputy head of the commission.